In modern multi-jet engine aircraft, a pilot may manually control the engine power by means of the throttle control levers or quadrants. In such aircraft, the throttle control is integrated with the flight control system and under normal flight conditions controlled thereby. It is essential, however, that in an emergency situation, such as a windshear warning or tower command, that the pilot immediately take over control of the aircraft. It is also essential that the manual control lever be coupled to the flight control system when the system is in automatic operation so that the lever assumes and maintains the proper setting for any future manual take-over.
A prior art auto throttle system is described in the U.S. Patent of Dressler et al., No. 5,188,316. In that system, a clutch mechanism employs a combination of wedge and roller elements to provide a positive clutch engagement and disengagement in response to a switch actuated solenoid. The solenoid is manually actuated and deactuated by means of a switch on the control lever and in an emergency, the solenoid can be deactivated by a sharp "bump" movement of the lever. The "bump" or sudden movement causes the lever itself to actuate a microswitch which controls the solenoid.
In many of the more modem jet aircraft, the engine control is accomplished electronically or by fiber optics. In such systems, sometimes referred to as "fly by wire" or full authority digital engine control (FADEC), the position of the power levers is sensed by a rotary component and a signal is then transmitted to the full authority digital engine control. Since the power levers only drive a rotary sensor in such systems, there is little or no feel to the pilot as found in conventional control systems wherein the throttle lever moves a relatively long cable. For this reason, it has been customary to add a friction brake to the power levers to provide this feel.
One example of the addition of a friction dement is contained in the U.S. Pat. of Meenen, Jr., No. 4,907,970. In that example, a slip clutch is used to resist fore/aft movement, the clutch being adjustable for proper "feel" As disclosed therein, the feel is designed to accurately simulate the feel of a throttle control of an actual aircraft in a thrust control simulator.
It is now believed that there may be a significant market for an improved auto throttle system for FAYDEC equipped aircraft. It is believed that a significant market may exist for a throttle control system which incorporates a simple friction mechanism to provide for a servo input, to control the "feel" of a cable operated throttle control and in which the torque for moving the throttle control lever for and aft is essentially the same whether the servo is being overridden or not.
It is also presently believed that a throttle control system in accordance with the present invention has the aforementioned desirable features. Such systems may also be installed or FAYDEC equipped aircraft without disrupting the pilot's console. However, in a retrofit of such aircraft, it may be desirable to disconnect any brake which has been incorporated in the throttle mechanism. In addition, such throttle controls are believed to be of relatively compact size, of minimal weight, durable and relatively inexpensive to manufacture.